Luminescent materials that exhibit narrowband emission are vital for full-colour displays. Here, we report a thermally activated delayed-fluorescence material that exhibits ultrapure blue emission with full-width at half-maximum of just 14 nm. The emitter consists of five benzene rings connected by two boron and four nitrogen atoms and two diphenylamino substituents. The multiple resonance effect of the boron and nitrogen atoms induces significant localization of the highest occupied and lowest unoccupied molecular orbitals on different atoms to minimize not only the vibronic coupling between the ground state (S0) and the singlet excited state (S1) but also the energy gap between the S1 state and triplet excited state (T1). Organic light-emitting diode devices employing the emitter emit light at 469 nm with full-width at half-maximum of 18 nm with an external quantum efficiency of 34.4% at the maximum and 26.0% at 1,000 cd m−2.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
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This study was supported by the ACCEL (JPMJAC1305) and CREST (JPMJCR18R3) programmes from the Japan Science and Technology Agency (JST), a Grant-in-Aid for Scientific Research on Innovative Areas ‘π-System Figuration’ (JP17H05164) and a Grant-in-Aid for Scientific Research (JP18H02051) from the Japan Society for the Promotion of Science (JSPS), Iketani Science and Technology Foundation and Mitsubishi Foundation. Preliminary measurements for the X-ray crystal structure analysis were performed at BL40XU in the SPring-8 with the approval of JASRI (2016A1052, 2016B1059, 2017A1132, 2017B1073, 2018A1114, 2018B1125) and with the help of N. Yasuda (JASRI). The authors thank T. Matsushita, K. Shiren, R. Kawasumi (JNC Petrochemical), Y. Honda (HPC Systems) and S. Nakatsuka (Kwansei Gakuin University) for valuable input.
The authors declare no competing interests.
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